Applied Mechanics and Materials Vols. 121-126

Abstract: In this paper, we analyse the structure of third-party logistics cost. We specially analyzes influence factor of transportation cost which account for 1/3 to 2/3 of the third-party logistics from the view of system dynamics. We establish the system dynamics model of transportation cost, and further more, we give the Vensim equations and explanation for it.

Abstract: This paper presents the modeling of stereo vision measurement for solving the optimal spatial point under non-ideal circumstances, and then analyzes the error of stereo vision measurement system from the imaging feature location and camera internal parameters and external parameters, such as the focal length, the baseline distance, which plays a important role in optimization of system architecture and layout of measurement system.

Abstract: Project group is characteristic of dynamic uncertainty and higher complexity ，which decides its management methods need to have enough flexibility. Based on the analysis of the flexible influence factors of the project group of management, the paper constructs the project group management flexibility evaluation index system, introduces fuzzy comprehensive evaluation method to the evaluation, and in order to increase its objectivity and feasibility ures the gray correlation analysis method to determine the weights during the process of solving. Finally provides an application example to show that the method is effective and practical.

Abstract: Wavelet Neural Network (WNN) is a new form of neural network combined with the wavelet theory and artificial neural network. The wavelet neural network model based on Morlet wavelet and the corresponding learning algorithm were studied in this paper. And through learning the wavelet neural network model is applied to all kinds of engineering examples, it proved that the wavelet neural network prediction model which has a more flexible and efficient function approximation ability and strong fault tolerance, and with high predicting precision.

Abstract: with the development of finite element technology, finite element model is becoming to the main analysis tool. However, because some theoretic assumptions, unsuitable constraint and uncertain material property are applied, the simulation result of finite element model isn’t different from the testing data. In order to improve the design quality and safety of spacecraft, this paper deduced the formula of spacecraft finite element updating, developed the spacecraft finite element model updating system, the software mainly of five parts: the frequency response function calculation, the loading inverse solution, the finite element model updating, the data display, virtual experimentation. Software can complete exciting force inverse, parameter sensitivity analysis, parameters screening and finite element model updating. The calculation result of updated finite element model is in accordance with testing curve shape on the main vibration direction, first-order frequency error is ±5%, response error is ±10%. Software meet the need of finite element model updating, it provide a software base for spacecraft design.

Abstract: Failure rate functions were usually constructed in terms of life distribution. The present paper defines “discrete failure rate”, analyzes the dependence of failure rate curve shape on the probabilistic property of load-strength interaction, and develops load-strength-interaction based system failure rate model. For the majority of mechanical equipment, operation load is normally a random process, components are subjected to a large number of stochastic load actions during its service life. Meanwhile, material property degrades continuously owing to the failure mechanisms such as fatigue. It is the ever changing load-strength relationship that yields the variation in failure rate. Based on the criterion that failure occurs when a load higher than the relevant strength appears, failure rate model is developed based on the interaction mechanism between load and residual strength, and their statistical characteristics as well. Based on the interpretation to the variation of failure rate in terms of load uncertainty and strength uncertainty, the effect of statistical risk of load and the effect of strength degradation on failure rate curve shape are highlighted.

Abstract: Based on the linear-elastic fracture theory, the fracture damage of gear structure is studied. By using the professional fracture analysis software FRANC3D, a three-dimensional propagation analysis is investigated for tooth root crack in involute gear, and also solving the three types of stress intensity factor(SIF) in tooth root semicircle crack tip, its changing rule and the 3D stress intensity factor formula are obtained. On this basis, a simulation analysis and study is conducted on propagation route of 3D tooth root crack, and the correctness of the analysis results is verified by comparing with the experimental results. Finally according to the mutation of maximum stress intensity factor in the crack tip，the fracture damage of gear teeth is predicated, and its working life is forecasted. By analyzing the different crack size, it is concluded that crack propagation velocity is very sensitive to crack initial length; initially, crack propagation slowly grow, with the increasing of crack length, the crack propagation will rapidly accelerate. The cycle life of fatigue crack in involute gear is about 1.85E5 times. All these findings have important significance for life estimation and failure detection of gear.

Abstract: To meet the requirement of high tracking accuracy as well as develop more reasonable evaluation method, in this paper, the General Regression Neural Network (GRNN) has been applied to build the tracking error model of the theodolite. First, we analyze the nonlinear factors in the theodolite. Second, we discuss the principle of GRNN, including its structure, the function as well as its priors. Third, we build the tracking error model based on GRNN and verify the model through the different parameters. The result indicated that the network model based on GRNN has high accuracy and good generalization ability. It could instead the real system to a certain extent. The research in this paper has important value to the engineering practice.

Abstract: Accompany with fast development of location technology, more and more trajectories datasets are collected on the real applications. So it is something of value in the theory and applied research to mine the clusters from these datasets. In this paper, a trajectory clustering algorithm, called Density-Based Spatial Clustering of Application with noise (Tra-DBSCAN for short), based on DBSCAN that is a classic clustering algorithm. In this framework, each trajectory firstly partitions into sub-trajectories as clustering object, and then line hausdorff distance is used to measure the distance between two sub-trajectories. Next, DBSCAN is introduced to cluster sub-trajectory to form cluster area, and then connecting different moments of clustering area is regarded as trajectory movement patterns. Finally, the experimental results show our framework’s effective.

Abstract: In the paper, two-dimensional Tunnel seismic Wave field is Simulated with finite element method, and the in the tunnel model with fault zone load Ricker wavelet source on the workface, compared the case of wave propagation according to wave field snapshot and time record, can intuitively, accurately reflect the characteristics of seismic wave propagation in tunnel seismic prediction with geological disasters such as the fault zone and so on.